cad – How to make straight horizontal runoff surface in mold design? Autodesk Inventor 2025

I have slightly bended detail, and i tried to make a mold for it.

In Mold Design we have a step called “Create Runoff Surface” aka Parting Line > place where Core and CAvity meets.

Problem: Inventor finds only part lines, which are bended > i cant make clear horizontal runoff surface with them. How to make straight horizontal Runoff Surface with bended detail?

What have i already tried:

• make a split in .ipt detail file with plane and then created a new Mold file with it/ Mold file does not recognize central split line
• make a plane in mold file, Create runoff surface doesnt recognize plane